This invention relates to phosphoric acid esters and their salts, to paints and molding compositions containing them, to the use of these phosphoric acid esters and salts as dispersants, and to solids coated therewith.
High mechanical forces are needed in order to incorporate solids into liquid media. To reduce these dispersing forces it is common to use dispersants which facilitate incorporation of the solids into the medium. These are generally surface active substances, also called tensides, having an anionic, cationic or non-ionic structures. These substances are either applied directly to the solid in small amounts, or they are added to the dispersing medium. The difficulty of dispersion is reduced by such a tenside. It is furthermore known that such solids can tend to reagglomerate after the dispersing process due to mutual forces of attraction, which nullifies the previously expended dispersing efforts and leads to problems.
Unsatisfactory dispersion manifests itself in an increase in viscosity in liquid systems, loss of gloss and changes of color in paints and coatings, unsatisfactory coloring power in pigmented molding compositions, and reduction of mechanical strength in reinforced plastics.
Also, an important factor is the high viscosity of liquid systems having a high solids content. To operate economically, an attempt is made to keep the solids content of such solid-containing dispersions as high as possible in the dispersion, combined with the lowest possible viscosity of the system that is to be dispersed. This is of particular importance in liquid synthetic resin systems, such as unsaturated polyester resins, for example, in which a very low initial working viscosity is desired with the highest possible solids content.
Phosphoric acid esters having various structures have been disclosed, for example, for dispersing or treating pigments. U.S. Pat. No. 4,456,485 describes acidic or neutral phosphoric acid esters of fatty alcohols and alkoxylated fatty alcohols as agents for treating specific blue pigments (alkali blue). Likewise, European Patent Application No. EP 256,427 describes the use of previously known phosphoric acid esters of alkoxylated fatty alcohols for preparing pigment dispersions suitable for aqueous applications. U.S. Pat. No. 4,720,514 describes pigment dispersions made using phosphoric acid esters of alkoxylates having various structures. German Patent Application No. DE 2,726,854 describes phosphoric acid esters of polyols used as dispersants in aqueous media or as detergent builders. These phosphoric acid esters are of a very complex nature and also contain free hydroxyl groups which originate from the epoxides that are used. They are evidently of a polyvalent nature with respect to the free phosphoric acid groups present in the molecules. U.S. Pat. No. 4,717,424 starts from carboxyl group containing phosphoric acid esters which in addition to the phosphoric acid group contain a free -COOH group in the molecule. These are not polymers. These products are used for stabilizing metal pigments against attack by water. U.S. Pat. No. 4,698,099 describes pigment dispersions containing phosphoric acid esters of monohydroxy-terminated polyesters as dispersants.
In may cases, good results can be obtained with the phosphoric acid esters described above. However, these compounds are not widely usable in modern binding resins and plastic systems, such as for example in high-solids paints, aqueous paints, systems which can be hardened by ultraviolet and electron beams, or LS-SMC or LP-SMC molding compositions (low-shrink or low-profile sheet molding compositions).
In a number of different systems, these compounds are not sufficiently compatible. This leads to inadequate dispersion due to insufficient interaction with the surrounding medium, and in many cases to precipitation phenomena and the associated dulling, spotting and increased viscosity.